The present invention relates to cyclones used for dust collection, and, in particular, to cyclones which are used to return particulate material to a fluidized bed.
In the prior art, many fluidized beds have a plurality of cyclones connected in series, so that particulate-laden gas passes through the first cyclone, where much of the particulate material is removed from the gas and is returned to the bed, then passes through the second cyclone, where some more of the particulate material is returned to the bed, and possibly through a third cyclone, where additional particulate material is returned to the bed. So, in this typical situation, the same gas passes through all the cyclones, and there is approximately the same gas flow rate through all of the cyclones.
The particulate material that is being returned to the fluid bed is often a catalyst, which is very expensive, so there is a great financial benefit to recovering the particulate material.
The cyclones consume a large amount of energy, which is expensive. They also encounter problems in that, instead of sending captured particulates down the dip leg of the cyclone into the fluidized bed, sometimes they draw particulates up the dip leg from the fluidized bed, which greatly reduces their efficiency.